Determining the Water Potential of a Potato Chip
Aim: To determine the water potential of a potato chip
Background knowledge
What is water potential?
Water potential is the measure of the tendency of water to move from
one place to another. Like the movement of water from potato chip to
surrounding solution or vice versa. Water always moves from an area of
high water potential to a region of lower water potential.
The addition of solutes decreases water potential making it more
negative. Therefore it is less likely to move from one place to
another. Pure water has a water potential of zero, by adding solutes
you make the water potential more negative. In plants water potential
depend on two things, Osmotic potential (due to presence or absence of
solutes) and pressure potential (due to turgor pressure).
To work out water potential you use this equation
Water potential = solute potential + pressure potential
Ψ = Ψs + Ψp
In my experiment the water potential equals the solute potential
(solute potential is always negative), as the pressure potential is
negligible. However pressure potential is pressure exerted when water
enters a cell and makes it turgid. Increasing pressure increases the
tendency of water to move, therefore increases water potential.
Pressure potential is always positive therefore making water potential
less negative. In my experiment I am not going to do anything to
affect the pressure, as this will disallow me to find the water
potential using the method I have selected.
What is osmosis?
Osmosis is the movement of water molecules from a high water potential
to a low water potential through a selectively permeable membrane.
This continues to happen to till dynamic equilibrium is reached and
the water potential on both sides of the partially permeable membrane
is the same.
Plant cells always have a strong cell wall surrounding them, which is
the selectively permeable membrane. When water moves in to the cell by
osmosis it starts to swell, but the cell wall prevents it from
Investigating Osmosis in Potatoes Aim: Investigate the movement of osmosis through a selectively permeable membrane, in this case potato. Introduction: Osmosis is the movement of water through a semi permeable membrane. The water passes from an area of high concentration to an area of low concentration, until the two concentrations are equal in concentrations of water. Many cell membranes behave as semi permeable membranes, and osmosis is a vital part in the movement of liquids in living organisms, for example, in the transport of water from the soil to the roots in plants.
If the concentration of one side of the membrane is greater than the molecules will travel from the higher to lower concentration. Eventually there will be a dynamic equilibrium and there will be no net movement of molecules from one side to the other. Osmosis is the diffusion of water. Like diffusion, the water moves from a region of higher water potential to a region of lower water potential.
For the preparation of Part 1, pieces were cut from the potato and were blended. The prepared suspensions were broken cells of the potato used as the extraction. The process of the suspension was the homogenization of the organism and later was centrifuged so that some of the substances reached the bottom (insoluble particles) and used the liquid as the enzyme(Schultz, 2006). The enzyme was brown colored known as the catechol oxidase, and that product can be used to measure the reaction rate using a spectrometer (Schultz, 2006). We started with twice the volume of the stock, so for the case of Part 1 was to begin with 6 ml of full strength enzyme. Two test tubes were used for the dilution. The first contained 5ml of buffered catechol and the
to the marble chips. I will have 30 ml of mixture and split it in to
Osmosis in Potato Tubes Osmosis: Osmosis is the movement of water molecules through a semi-permeable membrane from a high concentration to a low concentration. Diagram: [IMAGE] [IMAGE] Aim: To see the effects of different concentration of sugar solution on Osmosis in potato tubes. Key factor: In the investigation we change the sugar solution from: 0%-10%-20%-30%-40%-50% this is the independent variable; the dependant variable is the change in mass. Prediction: I predict that all the potato tubes in pure water or low concentration sugar solution will swell because water enters their cells by osmosis.
In osmosis, water can travel in three different ways. If the molecules outside the cell are lower than the concentration in the cytosol, the solution is said to be hypotonic to the cytosol, in this process, water diffuses into the cell until equilibrium is established. If the molecules outside the cell are higher than the concentration in the cytosol, the solution is said to be hypertonic to the cytosol, in this process, water diffuses out of the cell until equilibrium exists. If the molecules outside and inside the cell are equal, the solution is said to be isotonic to the cytosol, in this process, water diffuses into and out of the cell at equal rates, causing no net movement of water. In osmosis the cell is selectively permeable, meaning that it only allows certain substances to be transferred into and out of the cell.
This occurrence can be explained through the process of osmosis. The increase in mass as well as the increase in turgidity, in the potato tubes immersed in low sodium chloride concentration solutions is understood to be a hypertonic. Since the solution is hypertonic, the water molecules will diffuse into the area of lower water concentration (the potato tube) in order to achieve equilibrium. Alternatively, the decrease in mass in the potato tube submerged in highly concentrated sodium chloride solutions can be explained by its immersion in a hypotonic solution. As sodium chloride solution is less concentrated in water molecules than the potato tubes, the decrease in mass and loss of turgidity results from the net movement of water leaving the potato tube, which is higher in osmotic pressure, and diffusing into the solution.
The Effect of Water Concentration on the Mass of Potato Tissue Aim: The aim of this investigation is to discover the effect of water concentration on the mass of potato tissue, and also to investigate the movement of osmosis through potato tissue. Scientific Knowledge: When a substance such as a sugar dissolves in water, the sugar molecules attract some of the water molecules and stop them moving freely. This, in effect, reduces the concentration of water molecules.
If a plant cell is places in a hypotonic solution the cell has a lower water concentration to that of the solution. Water will move into the cell by osmosis from a high water concentration outside the cell to a lower water concentration inside the cell through a selectively permeable membrane. The cell becomes turbid
The. So if there is a lot of salt dissolved into water surrounding the organism (in this case a potato chip) then water particles from. other cells are going to attempt to equal the concentration of water. in the solution with the water concentration in the cell. Therefore most of the water from the cells of the potato chipping will change in mass, depending on the concentration of solution.
Once upon a time, in a kingdom far away far away… actually it wasn't that far away, the kingdom is currently known as Oregon, but this story starts in the year 1256.
Equipment Potato, Borer, Beakers, Measuring Cylinder, Stopclocks, Distilled Water, Electronic Balance, Salt solutions of various concentrations. Diagram [IMAGE] [IMAGE] [IMAGE] When we leave the potato in the solution for the allocated time, water
there would be no flow of water into or out of the cell so the cell
potato cells. In order to find the best way to do this experiment I am
Operation: A hydrometer is a measurement instrument used to measure the relative density of liquids, the ratio of a density of a liquid to the density of water.